In the Italian capital, thousands of tourists have been
disappointed to discover the Colosseum, one of the city's most
popular attractions, is closed to visitors, while checks are
carried out to determine the extent of the damage and to help
prevent further movement.

"It's an enormous quantity of
snow compared with what we normally get in winter
and it's had a
heavy impact, the equivalent of a flood."

- Gabriele Cavalera

Rossella Rea, archaeologist and superintendent of the Colosseum,
told CNN: "Tests and evaluation of the damage is still ongoing,
especially on the second level of arches."

Rea said the enforced closure of the site would have a serious
financial impact -- the Colosseum attracts some 7,000 visitors a
day, paying 12 euros for a ticket -- but that it was necessary in
the circumstances.

"At the weekend, some of the tourists didn't understand why the
Colosseum was closed -- for people from northern countries, the
snow is not a problem.

"But it's very unusual for us and it caused the detachment of
dust, concrete and bricks. Little quantities but if they fall from
a certain height they can be dangerous."

Cristiano Brughitta, spokesman for Italy's Ministry for Cultural
Heritage and Activities, said the damage was caused by ice forming
on the walls of the monument.

CNN Photo

"When the temperatures drop below zero, and there is rain and
snow, it causes ice to form which, with the increase in volume,
pushes the external plaster masonry and causes small pieces to fall
off," he said.

David Pickles, senior architect at English Heritage, told CNN
such damage was an extreme version of the natural wear and tear
buildings face during everyday weather.

"There's a whole freeze/thaw cycle of damage to buildings where
moisture gets into the stonework, into the pores of the stone, it
then freezes and expands very significantly, it then breaks up the
stone and then when it thaws, bits of stone will start falling
off.

"That's happening all the time, of course, that's one of the
major decay mechanisms in historic buildings anyway, because
they're largely water permeable... You can't treat stone to stop it
happening."

The town's Duomo (cathedral) is also shut, because of
water damage. Checks are being carried out on vulnerable buildings
in the area.

"Our biggest worry is the buildings in the historic center,
which have wooden joists and delicate roofs," said Gabriele
Cavalera, a spokesperson for the local council.

According to Cavalera, residents of some private homes in the
historic center are adding extra support to the old roof beams in
an attempt to prevent any further cave-ins.

"It's an enormous quantity of snow compared with what we
normally get in winter and it's had a heavy impact, the equivalent
of a flood," said Cavalera.

Brughitta agreed that conditions were exceptional: "Maybe every
30 years it gets this cold, but it's very rare."

A number of Italy's historic monuments, including the Colosseum
and
Pompeii, have suffered in recent years from damage and
collapse.

The Colosseum, which is scheduled to reopen to the public
Thursday, is due to undergo
restoration works later this year with sponsorship from
luxury brand Tod's.

In case of similar snowfalls in the future, Brughitta in Rome
suggests using a type of cold-weather "blanket" for exposed
monuments such as the nearly 2,000-year-old Colosseum.

Though Pickles said such plans may be difficult, on a practical
level: "For a building like the Colosseum, I should think it would
cost a fortune to cover it, because we're talking about a huge wall
area."

And while delicate, these buildings are nonetheless tenacious
when it comes to adverse weather and acts of god.

After all, said Cavalera, The Ducal Palace in Urbino, which is around
500 years old and a UNESCO World Heritage Site, managed to resist
collapse during the earthquakes of the 1990s and is so far holding
out against the snow.